Comparative Analysis of Carbon Emissions from Cement and Lime Fly Ash Stabilization of Pipe-Jacking Waste Soil Improved with Polyacrylamide and Sodium Bentonite

Abstract

This study conducted a comparative analysis of the carbon emissions resulting from cement and lime fly ash stabilization for pipe-jacking waste soil that has been improved with polyacrylamide and sodium bentonite. The unconfined compressive strength values under different mix ratios were experimentally determined and combined with carbon emission data, and the life cycle assessment (LCA) method was used to evaluate the engineering performance of cement and lime fly ash in the stabilization of pipe-jacking waste soil. The study revealed that the carbon emissions from cement-stabilized pipe-jacking waste soil required to achieve the same strength were lower than those from lime fly ash-stabilized pipe-jacking waste soil. This is mainly attributed to a smaller amount of cement significantly enhancing the strength of stabilized pipe-jacking waste soil. The research results indicated the following. (1) Within a default transportation range of 500 km, to meet the engineering strength requirement (7-day strength), the lowest carbon emissions, 2822.5 KgCO2e, were produced by transporting 50 tons of pipe-jacking waste soil stabilized with 9% cement by rail. Conversely, the highest carbon emissions, 14645 KgCO2e, were produced by transporting 50 tons of pipe-jacking waste soil stabilized with 30% lime fly ash using a light gasoline truck. The optimal solution reduced carbon emissions by 80.7% compared to the worst case. (2) When only the stabilizing materials were transported within a 500 km range, the lowest carbon emissions, 2595 KgCO2e, were produced by transporting 50 tons of 9% cement by rail, which reduced emissions by 70.5% compared to the worst-case scenario.

Keywords: Pipe-jacking waste soil, Carbon emissions, Compressive Strength, Life cycle assessment